The ORTEC Model 276 Photomultiplier Tube Base and Preamplifier incorporates an integral low-noise preamplifier, a PMT base with voltage divider network, and a focus control for optimum performance in scintillation detector applications. The unit provides two outputs: the preamplifier output for energy analysis and the anode output for either timing or auxiliary energy analysis. The preamplifier is dc-coupled to simplify pole-zero cancellation in the main amplifier. A Test input accepts the output of a pulse generator to calibrate and test the preamplifier and the following system. The Model 276 has a diode protection network to prevent damage to the internal transistors due to sudden application or removal of high voltage to the unit. The Model 276 is powered from any ORTEC main amplifier or preamplifier power supply.

The Model 276 is directly compatible with most 10-stage PMTs that fit standard 14-pin sockets.

Nominally 5 µV/eV with 2- by 2-in. NaI(Tl) crystal and PMT gain of 106; the typical output for a 511-keV x ray with a 10-stage PMT gain of 105 will be ~250 mV.

Saturation Level

+10 V into an open circuit; +5 V into 93-Ω load.

Voltage Divider

Resistor-divider connected to 10-stage PMT base. Total resistance 1.49 MΩ, resulting in bleeder current of 0.6 mA with typical high voltage of 1 kV. The distribution is linear to all stages with the focus adjustment on the grid.

Related Equipment
+

A C-36-12 Cable is required for connection to a high-voltage supply. A C-24-12 Cable is recommended for connecting the preamplifier output to the spectroscopy amplifier. For timing signals from the anode, use a C-25-12 Cable.